The present invention relates to a method for automatic self-monitoring or checking the proper functioning of nondestructive test equipment, and more particularly, the invention relates to self-checking of ultrasonic test equipment operated on the basis of sequential test cycles wherein the self-checking may be run as a test cycle or cycles.
Ultrasonic test equipment as they have been used are tested as to their proper functioning to a limited extent only. Usually, the function of the circuitry is indirectly checked during initialization or calibration of the equipment under utilization of dummies, reference standards or the like. The proper function becomes in effect that function carried out under the particular conditions of adjustment of the circuit when cooperating with such a reference or dummy. An example for calibration is, for example, disclosed in U.S. Pat. No. 4,101,326. On the other hand, one tests usually the function of individual components only, and adjusts them in accordance with specifications but without checking the entire system as to all of its complete functioning. Practice has shown that malfunctions of and in complex test installation requires extensive search operations for purposes of fault isolation which procedure can be carried out only by particularly trained personnel and are more often than not rather time-consuming.
The function tests as carried out and usually limited to checking on the transfer function for particular amplitude inputs. Other criteria such as mechanical wear, unintended misalignments of mechanical components, long term aging and drift of electronic components, etc., are usually caught only when the installation is recalibrated and adjusted. "Creeping defects" or the like may well not be caught in that fashion but are "brushed over" simply by retuning, trimming or other adjustment. Mutually compensating defects and even severe defects which do not yet result in complete component failure may well not be recognized in that manner as long as the available adjustment ranges permit compensation.